Original wooden Bensen rotor blades?

[BrianInVa]

A Facebook acquaintance has a set of original wooden rotor blades from a Bensen glider. He says they’re in almost perfect condition and is wondering if they can actually still be used?

 

[GyroRon]

Cool find.

I probably wouldn't fly them. Not on a normal powered gyro, and not at altitude.

They might be just fine for use for training purposes. Back a few years ago, people learning to fly gyros would spend a bunch of time just taxiing the gyro on the runway up and down with the blades spinning... And eventually move to crow hops... Spend a little time looking up info on how people used to train with the non powered towed gyro gliders and if you could replicate that with powered gyro and limit yourself to on the ground or barely off the ground altitude then maybe using these blades would be a smart move. Why a smart move? ... Because there is a reasonably good chance that in your first couple hours of training you might have a incident that tears up your blades, and better to tear up a old cheap set than a new expensive set

 

[BrianInVa]

I’ve read that some wooden Bensen rotor blades have a metal spar that runs the length of the blade, sandwiched between the wood, that can only be seen by looking at the end of the blade, under the hub bar bracket.

It was said early wooden Bensen rotor blades did not have the metal spar but later ones did. If they have the metal spar, supposedly they can still be flown, even with a powered Bensen?

 

[Mayfield]

It is a steel strap inlet into the bottom of the blade and fixed with screws.

Jim

 

[BrianInVa]

It is a steel strap inlet into the bottom of the blade and fixed with screws.

Jim

Then it doesn’t look like these have the steel strap?

 

[WaspAir]

How old are those blades? Organic materials and old school adhesives have a shelf life that is not simple to determine and can also be very difficult to test non-destructively. Be very cautious.

 

[Mayfield]

How old are those blades? Organic materials and old school adhesives have a shelf life that is not simple to determine and can slso be very difficult to test non-destructively. Be very cautious.

Almost certainly glued with Resorcinol. Although great care must be made to ensure good mechanical fit, it has really good long term bonding qualities. Here's some info pulled from the web. It matches my memories of the glue. I built a couple of canoes, a light hydroplane (about 12 feet long and 4 wide at the trailing edge of the sponsons), and too many Bensen rotor blades, using Resorcinol. I'm certain I would recognize the smell immediately.

https://www.christinedemerchant.com/adhesive-glue-resorcinol.html

 

[BrianInVa]

It is a steel strap inlet into the bottom of the blade and fixed with screws.

Jim

Looks like it has the steel spar running the entire length. He double checked with a strong magnet.

 

[Doug Riley]

That's certainly A steel strap spar, but it's not a plans-built Bensen arrangement. Bensen's strap spar was thinner than that one (1/8" IIR). As has been said, it fit into a trough in the bottom of the blade. The inboard end of the spar formed the lower mounting strap.

The spar and its jillion flathead wood screws were visible if the blade was clearcoated; not so much if the blade was painted.

I'd stay away from those blades except as interior decorations, since they depart from the design that we know works. Flying them would put you deep in guinea-pig territory.

 

[Mayfield]

Yep, 1018 steel , 1/8" thick.

Jim